Locations

Organization

Rationale For Data Collection

Each season around the end of March, the ocean surface around Antarctica freezes to form sea ice. Close to the coast in some regions (e.g. near Mawson and Davis stations) this ice remains fastened to the land throughout the winter and is called fast ice. The thickness and growth rate of fast ice are determined purely by energy exchanges at the air-ice and ice-water interfaces. This contrasts with moving pack ice where deformational processes of rafting and ridging also determine the ice thickness. The maximum thickness that the fast ice reaches, and the date on which it reaches that maximum, represent an integration of the atmospheric and oceanic conditions. Changes in ice thickness represent changes in either oceanic or atmospheric heat transfer. Thicker fast ice reflects either a decrease in air temperature or decreasing oceanic heat flux. These effects can be extrapolated to encompass large-scale ocean-atmosphere processes and potentially, global climate change.

Measurement Technique

Tape measurements through freshly drilled 5 cm diameter holes in the ice at marked sites. Depth in meters were recorded daily.

Data Interpretation

At Davis, where the water depth near the station is relatively shallow, there is little heat transfer from the ocean to the ice, and the thickness is largely determined by atmospheric conditions, predominantly temperature and snow cover. At Mawson, where ocean depths are over 200 m, interannual variability of ice thickness is also influenced by changes in oceanic heat flux. Long-term statistics are maintained for each site of the date of ice formation, maximum thickness, date of maximum thickness, date of any mid-season breakouts, and date of final breakout of the fast ice. Incomplete historical records exist for Mawson back to 1954 and for Davis back to 1958.